The aim of the proposed work is to achieve a better understanding of the proliferative behavior and related properties of the neoplastic cells in different hematopoietic tumors. It is hoped that more complete information about cellular kinetics will permit not only formulation of more effective treatment schedules but will also lead to clearer definition of the fundamental abnormalities in the hematopoietic tumors and the interrelationships between them. Patients with acute leukemia and disseminated lymphoma will be studied before, during and following chemotherapy to determine what kinetic changes are caused by different drugs and with the goal of divising improved treatment schedules. Both autoradiographic methods employing H3-thymidine and continuous flow microfluorometric methods using DNA specific fluorescent stains will be used. Studies will also be conducted in vitro on established cell lines of human hematopoietic cells during their different growth phases and on fresh human normal lymphocytes and leukemic and lymphoma cells to determine the pertubations caused by different drugs and the influence of natural regulatory factors.